| dc.description.abstract | A series of tests on flexible model diaphragm walls embedded in an
overconsolidated clay was carried out at the London Geotechnical Centrifuge
Centre. The walls were propped at the crest and, following the simulation of
excavation, were propped at formation level. Although a retained height of 10m
was modelled in all tests, the depth of embedment below dredge level varied
between Sm, 10m and 15m. A 'softer' propping sequence was also investigated
with excavation to 5m below the retained surface prior to the installation of the
crest level prop then, following further excavation to dredge level, the bottom
prop was installed. The pre-excavation lateral earth pressure was also
investigated.
The background and use of twin-propped retaining walls is discussed together
'with the design of the centrifuge model and modelling procedure. The results of
the tests are presented and the effects of embedment depth, construction sequence
and pre-excavation lateral earth pressure coefficient is discussed.
A series of finite element analyses using the critical state soils program CRISP
was undertaken in which it was attempted to model the centrifuge models.
Generally, results were in reasonable agreement, although it was discovered that
the calculated wall movements and prop loads were sensitive to the slope of the
Hvorslev surface required for the Schofield soil model used in the analyses.
The prop loads from the centrifuge tests and finite element analyses were
compared with prop loads calculated using popular empirical methods and with
prop loads observed on site. Generally, prop loads were underpredicted using the
empirical methods which are unable to account for construction sequence effects
and probably overestimate the degree of lateral stress reduction that takes place
during excavation. | en_US |
